Cooling system for industrial ovens



y 1958 c. H, BARNETT $844,888-

COOLING SYSTEM FOR INDUSTRIAL OVENS Filed June 9, 1954 4 Sheets-Sheet lINVENTOR. CHARLES l-LflAR/VE 7'7 9 FT-.GR NEYS.

July 29, 1958 C. H. BARNETT 2,

COOLING SYSTEM FOR INDUSTRIAL OVENS 4 Filed June 9, 1954 4 Sheets-Sheet2- IN V EN TOR; C HA RLES H. BARNETT ow/v4 A T ramvms.

July 29, 1958 c. H. BARNETT COOLING SYSTEM FOR INDUSTRIAL OVENS 4Sheets-Sheet 3 Filed June 9, 1954 Q A r TOR/V575.

July 29, 19 58 I c. H. BARNETT 2, 8

COOLING SYSTEM FOR INDUSTRIAL OVENS Filed June 9; 1954 4 Sheets-Sheet 4/45 46 45 K 1 67 7b 4 G /5Z Q Q l j I INVENTOR. W CHARLES H. BARNETTgreatly increased: costs.

successively.

United, States Patent COOLING SYSTEM FOR- INDUSTRIAL OVENS Charles H.Barnett, Shaker Heights, Ohio, assignor to The Foundry EquipmentCompany, Cleveland, Ohio, a corporation of Ohio Application June 9,1954, Serial No. 435,445

8 Claims. c1. s4 20s industry to bake sand cores after the latter havebeen formed in core blowing machines. The baking process is-fairly slowand requires that the cores be-heated for a considerable period of timeat a fairly high temperature. This is usually accomplished in coreovensthrough which conveyors travel, supporting the cores. When thecores leave the oven, if no cooling means is provided, they are much toohot to be handled by workmen and, moreover, smoke very objectionably dueto oxidation of the binder material used with the core sand. For thisreason, core'ovens employedin large installations include a cooling zoneimmediately prior to emergence of the conveyor from the oven, and it isconventional .toblow relatively cool air into this portionof the ovenand across the moving cores. I The most practical form of oven has beenfound to be the vertical or tower oven as contrasted to the horizontaloven, but the present invention is adapted to each form.

Core ovens are very large and expensive structures and to extend such anoven even a few feet results in There is, accordingly, attemptation tokeep the cooling zone toa minimum, but unless adequate coolingfacilitiesare provided, theoven cannot be operated at maximum capacity.Sineethe cores-move continuously through the oven, the-efficiency of thecooling means employed :determines in large measure the permissible rateof production.

It :is among the objects of myinvention to provide an oven coolingsystem of increased capacity comprising a plurality of cooling stageseffective to bring work heated in the oven rapidly to a safe handlingtemperature without .the danger of thermal shock thereto. Incontinuouscore-ovens and the like, the plural stages of such system are-arrangedto besuccessively encountered by the moving cores following baking ofthe same and-prior to their .passage from the oven. 1

Another object ofthe invention is to provide such a cooling system whichproduces a plurality of distinct air currents of increasingly lowertemperatures in adjoining regionsofthe oventhrough whichithe heatedwork'moves It is also one of my objects to employ refrigerated air asthe cooling medium in the 'final, stage of-this system with the worktemperature'firstEbeinglowcred in a preceding stage or stagessufl'lciently to elimi mate the thermal shock which would *normallyresult if theheated work was initially contacted byilthe chille'd air.

- A further-object is to 'providepreecooling means for ovens havingdefined-heating and cooling zones,; distinct the workvtherebetween tto avalue. intermediate :the .re-

'-spective temperatures of-theadjacent endsofzsuch zones.

"ice

- Generally speaking, an oven cooling system is, for practical reasons,designed to handle average work or to meet the requirements of the workprocessed in greatest quantity and cannot normally be operated at itsdesign efficiency whena ,particular work lot presenting more exactingrequirements-is to be processed. For example, most commercial cores andformed of sand, and core ovens are adapted primarily to process articlesof this general composition with, of course, adequate flexibility totake care of the usual variations in size, shape and the likeencountered in normal operatiom However, for some uses, the cores areformed of plaster of Paris and these are extremely susceptible todestruction by thermal shock, more so than the sand cores. As a result,the normal temperature differential between the oven heating-and coolingzones, while not developing dangerous thermal shock in the case of sandcores may, nonetheless, be suflicient to damage and destroy plaster ofParis cores. Ordinarily, this could be avoided only by raising theaverage cooling temperature which, in turn, would require the workprogress to be slowed. The pre-cooling means of my invention, however,makes it possible to :maintain optimum operating conditions despite sucha change in the character of the work by reducing the abruptness of thedrop in work temperature on leavingthe heating zone and passing to thecooling zone.

Additional objects of the invention are: to provideautomatic.temperaturecontrol of the pre-cooling means set forth; toprovide a multi-stage cooling system of extreme flexibility, whereby theoperation thereof may readily be adapted as best suited for prevailingambient conditions; and to provide efiicient and readily controllableuse of the air in such system to the extent of reusing .air exhaustedfrom the oven when this affords best results. These and other objectsand advantages 'of the, invention will be apparent from the followingdescription.

To the accomplishment of the foregoing and related ends, theinvention,-.then, comprises the features hereinafter fully .describedand particularly pointed out in :the claims,-.the following descriptionand the annexed drawings setting forth in detail. certain illustrativeembodiments of the invention, these being indicative, however, of but afew .of the various ways in which the principle of the invention may beemployed.

In said .annexed drawings:

Fig. .1 -is ,an end elevational view of a continuous vertical-core oven.ortowerequipped with the improved cooling system of my invention;

Fig. 2 is a-side elevational view of this oven looking from the right-inFig. 1 or toward the'unloading side of the oven;

able height andhaving a continuous'conveyor, designated generally ,byreference numeral 1, movable therein to .transportthegreensand cores andthe like to be cured by baking. The tower-frame, made up of suitablestrucaturalwmembers, jlS preferably supported on the bottom of apitZ'beneath" the level of the. floor 3 of the building withinwhichitheoven-is situated, in order to conserve {9 height and affordworkmen convenient access to the conveyor at floor level.

The pit is enlarged somewhat laterally relative to the tower frame andsuitable flooring 4, for example a grating. is provided to bridge thepit opening around the base of the tower at the level of the floor.Beginning at floor level and extending vertically a sufficient distanceto allow safe head room, the tower frame is open and divided to form theloading station A and unloading station B respectively at the ascendingand descending sides of the conveyor, as indicated by the arrows showingthe direction of conveyor movement. The center passageway between thetwo stations permits workmen to enter therein and load the work fromboth sides of the loading station.

Secured to the remaining vertical extent of the tower frame above theloading and unloading stations are suitable insulating panels formingend walls and 6, side walls 7 and 8, and top wall 9. The frame is alsoclosed transversely at the approximate upper limit of the loading andunloading stations, partially by the furnace 10 and its bottomsupporting structure, with the result that this upper major extent ofthe tower forms a substantially completely closed chamber within whichthe Work may be treated.

The conveyor mechanism employed is conventional, and therefore, has beenshown, and will be described, only generally. It comprises twocontinuous chains, one of which is shown at 11 in Fig. 1, arranged toextend vertically in the respective end regions of the oven and aplurality of cross rods extending horizontally between the two chains atregular intervals therealong. Work carriers 12 in the form of pluraltray units are freely suspended on the cross rods at their approximatelongitudinal center lines so that, when properly loaded, the carrierswill normally be balanced about their connections with the rods. The twochains pass over drive sprockets, one being shown at 13, mounted on ahead shaft 14 in the top region of the oven and over a floatingstructural take-up 15 in the pit 2, the latter serving to guide andtension the chains at the lower turns thereof. At one end of theheadshaft 14 there is attached a large drive gear 16 adapted to bedriven by a suitable electric motor, not shown. headshaft is driven torotate the drive sprockets in a clockwise direction as viewed in Figs. 1and 3, thus providing the aforementioned ascending and descendingmovement of the work in the loading and unloading zones.

As shown in Fig. 3, a heat supply plenum 17 is arranged centrally of theoven and extends vertically from immediately above the furnace 10substantially to the headshaft 14. The side wall of the plenum facingthe ascending portion of the conveyor above the loading zone and theplenum top is provided with a plurality of horizontal ports 18 with theremaining walls thereof being closed so that air supplied the plenumwill flow out such ports and over the work as it ascends with theconveyor. Hot air at a temperature sufficient to cure or bake the greencores is fed to the plenum through the opening 19 in one end wallthereof in communication with the discharge side of a heat supply fan orblower 20. The intake air for this blower is drawn through duct 21passing through the furnace and is heated in this manner to the desiredtemperature. It will be understood that any suitable form of furnace,such as those now commonly used in core ovens, may be employed. A seriesof exhaust conduits 22 is provided in the upper region of the oven topermit a portion of the hot air circulated over the work to be exhaustedto the oven exhaust stack 23 and through the latter to the outsideatmosphere. Dampers 24 are desirably provided in these conduits toregulate the amount of hot air thus exhausted from the oven. At thedescending side of the conveyor a vertical wall 25 is provided risingfrom the top of the furnace to a height slightly less than that of theplenum in laterally In the construction illustrated, the' spacedrelation with the rear wall 26 of the latter. These two walls form therecirculating duct now commonly provided in core ovens of this type forreturning a portion of the hot air in the top of the oven to thefurnace. 1n the operation of the oven as thus far described, the greencores are placed on the Work carriers moving upwardly through theloading zone A by the workmen, from either or both sides of thisstation, and each loaded carrier then moves substantially immediatelyinto the heating zone of the upper enclosed oven chamber. In this zone,the hot air supplied by the blower 20 from the furnace to the plenumflows out the several ports 18 over the cores, and convectively in agenerally upward direction therewith. As noted, a portion of this airmay be exhausted through the stack 23 and a further portion drawn intothe recirculating duct for reheating and further use. The cores must bethoroughly and uniformly baked at a fairly high temperature related tothe conveyor speed or, in other words, to the length of time the movingcores are subjected to the hot air flow, and before the cores reach theunloading station they must be cooled sufliciently to permit safehandling by the workmen engaged in unloading the conveyor. Since thework is particularly sensitive to thermal shock, an abrupt drop in worktemperature must be avoided, while at the same time, adequately coolingthe same in a zone of limited extent. It would be obviously uneconomicalto increase the already substantial height of the tower for the purposeof lengthening the usual cooling zone, and hence the time the work is insuch zone, and my invention provides a rapid but safe cooling within thedimensional limits of conventional vertical core ovens.

Coming now to this cooling system, the physical structure thereof willfirst be set forth and the operation then discussed in connection withthe simplified flow diagrams of Figs. 4 and 5. Extending laterally fromthe unloading side of the tower are four platforms at differentelevations with the lowermost platform at the level of the bottom of theenclosed oven chamber and the uppermost in the region of initialconveyor descent. Supported on the uppermost platform 27 is a first fanor blower 28 having a conduit 29 connecting the outlet thereof to asupply boot 30 arranged against the tower side wall 8. The boot isgenerally rectangular, as shown, and that portion of the side wallcovered thereby is provided with a series of vertically spaced ports 31which lead to the upper end of the cooling zone. Connected to the inletof fan 28 is a duct 32 extending downwardly to a T- connection supportedon the next lower platform 33. One horizontal branch 34 extends only ashort distance from this connection and is open at its end 35 so thatambient air may be drawn therethrough. A second horizontal conduit 36extends from the connection about one end of the oven and then inwardlyto communicate with the recirculating duct. Thus the blower 28 alsodraws air from such duct, and this portion of the make-up air will be atan elevated temperature. A proportioning damper assembly 37 located inthe T-connection includes dampers 38 and 39 respectively operative toopen and close the branch lines 34 and 36 in varying amounts. The twodamper parts are interconnected for joint actuation.

A second fan or blower 40 is supported on platform 41 at the next lowerlevel and has connected to its discharge side a distributor 42 whichconveys the air impelled by the blower to a second supply boot 43. Thefirst supply boot 30 is, of course, of predetermined vertical extent,and the second boot 43 likewise extends a predetermined verticaldistance from a point closely adjacent the bottom of the boot 30. Thatportion of the tower side wall 8 covered by the second boot 43 also hasa series of vertically spaced openings or ports, shown at 44, todischarge air over a section of the cooling zone in operative successionrelative to that supplied with air from the first 75.

boot. A common exhaust means is provided to withdraw actress '5 the airsupplied the oven by both thefirs't 'and"v second boots through acoolair z'exhaust s't ack 45 vented to the outside atmosphere. This means.comprises a cooling air exhaust fan 46 having its 'outl'et connected tosuch stack and its inlet side 'to 'a common header 47 extendinghorizontally along the sidewall of the tower. At each end of the header,a recovery duc't 48 curves downwardly therefrom and extends verticallyto the approximate level of the bottom of the second boot 43. Aplurality of vertically spaced openings 49 is provided in each end wallof the tower and a series of short ducts 50 extend outwardly betweenthese openings and the respectively associated recovery ducts. It willbe apparent then that air impelled into the oven by the'b'low'ers 28 and40 will be caused to flow over the work in a generally upward directionand to be exhausted by the blower 46. The two currents of air thusproduced in successive sections of the cooling zone, therefore, flowgenerally in a direction opposite to that of the moving conveyor. Thelowermost platformSl at the terminal end ofthe cooling zone supports athird and final cooling blower 52 equipped with a distributor 53 tosupply air to a third supply boot 54. As with the other boot-s, supplyboot 54 overlies a predetermined area of the tower'wall and verticallyspaced ports 55 are provided in such area to communicate with thecooling zone. The air caused to flow in the end region of the coolingzone may be exhausted therefrom through openings '56 in each end wall,ducts 57 leading therefrom, and recovery ducts SSarran'ged similarly asthe exhaust means described in connection with-the first two supplyboots. ii l Here, however, the recovery ducts communicate with ahorizontal duct 59 which has a short connection 60 extending outwardlyat right angles to a four-way junction indicated generally at 61. Theupper vertical branch 62 of this junction leads to the inlet of blower40 while the opposite vertical branch 63 connects with the intake of theblower 52. The remaining duct =64'at this junction leads therefrom to aninlet stack 65 which extends vertically through the building roof,indicated '-by the dashed line 66, to permit outside air to be drawn inthrough its outer open end 67, and a damper 69 is positioned 'to beadjustably movable between'position's selectively opening and closingthe opening 68 and that-portion'of the stack above such opening. Thus,the stack can supply air from both within and without the building inwhich the oven is located in adjustable relative amounts depending onpositioning of the damper69.

Since the four-way junction 61 connects 'with'th'e intakes of theblowers '40 and 52, air may be drawn from both the inlet stack 65 andthe *exhaust header 59. A supply damper 70 is positioned in thisjunction to regulate adjustably the distribution or division of the'a-irfrom these two sources between the blowers 40 and 52.

A further, and important, feature of the construction I is the inclusionof means for refrigerating theair-circulated by the blower 52 in "thefinal cooling stage just before the work passes from the oven enclosureto the unloading station. To this end, the branch 63 extending betweenthe junction 61 and the blower 52 is wrapped with coils 71 through whicha suitable refrigerant is circulated from a conventional' motorcompressorunitshown at 72. Regardlessof the source of'the intake air forthis final blower, such air will, therefore, be chil'led before the sameflows over thework.

With reference to Fig. 4, the operation of -*the precooling means of theinvention will 'inowbe described, it being first :noted that thismeansis operative in the region of initial conveyor descent or betweenthe heating zone and the cooling zone proper. -='Since the air drawn inby theblower 28 is taken both from-the ambient atmosphere and therecirculating du'c't,=it will'ibe apparent that the temperature of thecombined air will be'in excess of the ambient air temperature. Thistemperature :should lie between the temperature at theend of theheat- 6ing zone and that at the beginning of the cooling zone proper to reducethe 'abruptness of the temperature drop which would normally obtaintherebetween. Control of the supply air temperature may be had byadjustment of the blending damper 37 which determines the relativeamounts of ambient air and air drawn from the recirculating duct makingup the intake flow. This control is preferably made automatic by meansof a thermocouple,

73, or other comparable temperature sensing element, and a smallreversible motor '74 operative to rotate the damper shaft. An indicatinginstrument 75 is provided between the thermocouple and motor so that thetemperature is indicated visually, and the thermocouple is'prefera'b'lylocated in the lower or advance end of the precoolingzone. As indicatedby the arrows, a portion of the air circulated in this zone will flow tothe top of the oven, but the major portion will be exhausted through theblower 46 and the stack 45.

Inthe first or pre-cooling stageof my cooling system, the worktemperature is, therefore, reduced only a relativelyslight amount topermit the processing of certain work which may be more susceptible thanusual to damage by thermal shock. Plaster of Paris cores have alreadybeen mentioned as an example of such work which, without the pre-coolingmeans I provide, cannot be handled safely at the same rate as the sandcores more commonly processed. Immediately following precooling'of thework in this manner, the work as moved by the'conveyor passessuccessively through two further cooling stages afforded by that part ofmy system shown in Fig. 5.

The-second cooling stage is effective over an area indicated by the box76 in the cooling zone, while the third and final stage is representedby the box 77. The air circulation is generally shown by the arrows inFig. 5 with the dampers 69 and 70 respectively in their full linepositions. With this condition of the dampers, 'air taken in fromoutside the building through the stack opening 67 andfrom beneath theceiling through the opening 68 flows to both the blowers 40 and 52. Bothblowers also draw exhaust air through duct 60 from the lower coolingregion 77. The air taken in by the blower 52 is, of course, chilled bythe refrigerating coils 71 and some of this air is recirculated afterpassing over the work in a direction generally opposite to the movementthereof, and some flows'to the blower 4t).

I-twill be seen that the air flowing in the second stage will be athigher temperature than that caused to flow in the refrigerated stage.By adjustment of the dampers 69 :and 70, the circulation of air in thesetwo stages may be considerably modified without upsetting the desiredtemperature relation thereof which affords a progressive cooling. Theflexibility of the system permits it to be readily adapted to varyingclimatic conditions and of the many obviously possible combinations ofdamper thereof,all this hot air may be fed to the blower 40 andclrcula'ted thereby over the work in an upward direction before beingexhausted by blower 46. In the region 76,

therefore, the work is subjected to a cooling flow of fairly warmambient air. In its position 79, the damper 70 also causes all theexhaust air flowing through the conduit'60 to be returned to the blower52, and thus all this air is again refrigerated and recirculated. This.redu'ces the load on the refrigeration unit, since it is required torefrigerate only the relatively cool exhaust air.

For'winter operation, the damper 69 may be movedto the dotted lineposition 80 and damper 70 to its dotted line position 3'1. fWith theseadjustments, cold outside air 'Wlll bc drawn in and supplied completelyto the blower 52, while all the cool exhaust air from the conduit 60will How to the inlet of the blower 40. Again this atrangement providesa minimum load on the refrigeration unit, since the outside air willusually be at a lower temperature than the cool exhaust air. It will benoted that in both the summer and winter operation, the work is firstsubjected to a counter flow of cooling air at a temperature higher thanthe temperature of the chilled air it encounters in the final coolingstage. Since the refrigerating coils are operative in the branch linebetween the four-way connection 61 and the blower 52, the minimumcooling temperature will always obtain in the final stage.

The use of refrigerated air permits the work to be cooled rapidly whilethe preceding stages may be controlled to lower the work temperaturesufiiciently to avoid any thermal shock. Within this general operation,the system is extremely flexible and readily controlled. For example, itfor some reason the conveyor is driven at slow speed with only a smallcore production, the second cooling fan may be driven without, however,refrigerating the air supplied thereby. In order to realize maximumproductivity, however, the refrigeration unit will be energized withpreliminary cooling of the work in one or both of the two precedingstages. understood that the Cooling system is not limited either to coreovens or to continuous vertical core ovens, and may be used to equaladvantage in other industrial ovens where it is desirable or necessaryto provide cooling in a plurality of stages.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims, or the equivalent ofsuch, be employed.

I therefore particularly point out and distinctly claim as my invention:

1. A cooling system for an industrial oven in which work being processedis moved in a predetermined path, comprising a series of three blowersequipped with distributing means for flowing air over the work as itmoves in the oven and arranged to be operative successively with respectto the moving work, air intake means for the first such blower operativeto supply ambient air thereto after first subjecting such air to heatfrom the oven to warm the same, inlet mean for supplying the secondblower with ambient air selectviely from within and without the buildingstructure in which the oven is located, refrigeration means for chillingthe air supplied the oven by the third blower, and means forrecirculating at least a portion of the air flow produced in the oven bythe third blower after passing over the work and again being chilled bysaid refrigeration means.

2. A cooling system for a continuous core oven in which the cores aremoved therethrough by conveyor means, comprising a first bloweroperative to flow air over the cores in a pre-cooling zone followingimmediately the oven heating zone, air intake means for said firstblower including a passage in communication with the heating region ofthe oven and an inlet for ambient air, inlet damper means for adjustablyregulating the relative amounts of heated and ambient air thus suppliedthe first blower, a second blower operative to flow air over the coresafter the same have passed through such pro-cooling zone, a third blowerhaving refrigeration means operatively associated therewith for flowingchilled air over the cores in a final cooling stage, supply duct meansconnecting the inlet sides of said second and third blowers, an inletstack extending from said duct means outside of the building structurewithin which the oven is located, an opening in said stack within suchbuilding structure, means for adjustably regulating the air taken inthrough said stack from within and without the build- .ing structure, anexhaust conduit also connected to said supply duct means for returningthereto the air discharged It will he in the oven by said third blowerafter the same has flowed over the cores, and supply damper means for adustably controlling distribution of the air delivered to the supply ductmeans by said inlet stack and exhaust conduit between the second andthird blowers.

3. In a conveyortype industrial oven, a cooling system comprisingfirst'and second blowers each producing a distinct flow of cooling airover the work as the same connected to said supply duct and extendingtherefrom through theroof of the building structure within which theoven is located forsupplying outside air, an aperture in said stack justbeneath the building roof, inlet damper means for adjustably opening andclosing said aperture and the stack portion thereabove, whereby theinlet air may be drawn selectively from under and outside the roof, anexhaust duct also connected to said supply duct for withdrawing the airdischarged to the oven by said second blower, supply damper meansoperative adjustably to direct the inlet air and air from said exhaustduct between the two blowers, the supply damper meansin one conditioncausing all inlet air to flow to the secondblowerand all such exhaustair to the first blower, and, in another condition, causing the exhaustair to be completely recirculated to the second blower and all inlet airto flow to the first blower, and means for refrigerating the airdischarged to the oven by said second blower, the cooling system thusproviding adjustable, but gradual, cooling so that the work may bebrought rapidly to handling temperature without the danger of thermalshock thereto.

4. In a conveyor type industrial oven, a cooling system comprisingfirstand second blowers each producing a distinct flow of cooling air overthe work as the same is moved in the oven by the conveyor, said blowersbeing arranged in operative succession relative to the heated movingwork so that the latter is subjected to the air flow produced by thefirst blower and thereafter to that produced by the second blower, aninlet stack connected to the inlet side of said first blower andextending therefrom to the outside of the building structure withinwhich the oven is located, an opening in the portion of said stackwithin the building, inlet damper means adjustably operative to regulatethe flow of air through said stack from both inside and outside thebuilding, exhaust duct means for Withdrawing the .air supplied the ovenby said second blower and returning at least a portion of the samethereto for recirculation, and means for refrigerating the airdischarged by said second blower to the oven, whereby the work afterfirst being subjected to a cooling flow of ambient air is further cooledby chilled air.

5. In a conveyor type industrial oven adapted to process cores and thelike which are particularly sensitive to thermal shock, a cooling systemoperative to cool the cores in two stages after the same have been movedby the conveyor through the heating zone of the oven, said coolingsystem comprising a first fan, an inlet conduit adapted to supplyambient air to said fan from a region proximately beneath the ceiling ofthe building structure within which the oven is located, a supply bootcon nected to the outlet of said fan so constructed and arranged as todeliver the ambient air impelled by the fan to the oven over apredetermined extent of the conveyor travel, a second fan, duct meansfor circulating air through said fan and toe section of the conveyortravel in operative advance of that in which the ambient air deliveredby said first fan flows, refrigeration means for cooling the aircirculating in said duct means, whereby ,the heated cores after firstbeing cooled by ambient air are furthercooled bychilled air, and exhaustmeans for withdrawing the chilled air discharged in the oven andreturning the same to said duct means for recirculation.

6. In a conveyor type industrial oven adapted to process cores and thelike which are particularly sensitive to thermal shock, a cooling systemoperative to cool the cores in two stages after the same have been movedby the conveyor through the heating zone of the oven, said coolingsystem comprising a first fan, a supply boot connected to the outlet ofsaid fan so constructed and arranged as to deliver air impelled by thefan to the oven over a predetermined extent of the conveyor travel, asecond fan, an inlet conduit adapted to supply said second fan with airfrom outside of the building structure within which the oven is located,duct means for discharging air from said second fan to a section of theconveyor travel in operative advance of that in which the air from saidsupply boot flows, refrigerating means for chilling the air thuscirculated by said second fan, and means for exhausting the chilled airfrom the oven after flowing over the heated cores in such section of theconveyor travel and delivering the same to the inlet of said first fan,the chilled air having been warmed by its extraction of heat from thecores before passing to the first fan, whereby the cores are subjectedto a flow of relatively warm air for a predetermined extent of theirmovement before encountering air at the minimum refrigeratedtemperature.

7. In an industrial oven including a housing, conveyor means for movingthe work to be processed through such housing, and means for heating thework in a portion thereof; a cooling system comprising first and secondblowers having their outlets in spaced relation in the housing at asucceeding portion of the same, refrigeration means in the outlet ofsaid second blower for chilling the air discharged in the housingthereby, supply duct means connected commonly to the intakes of thefirst and second blowers, recovery duct means in the housing forreturning at least a portion of the chilled air supplied by the secondblower to said supply duct means after passing over the work, branchduct means connected to the supply duct means and being open externallyof the oven for entry of ambient air, and damper means in the supplyduct means for adjustably regulating the division of the ambient air andair recovered from the housing by the recovery duct means between saidfirst 10 and second blowers to maintain a predetermined temperaturedifferential in the respective discharges thereof. 8. In an industrialoven including a housing, conveyor means for moving the work to beprocessed through said housing, and means for heating the work in aportion of the housing; a cooling system operative in a succeedingportion of the housing to cool the work to a safe handling temperatureprior to exit from the oven, said cooling system comprising a series ofthree blowers each equipped with air distributing means, the latterbeing arranged in the housing along the path of work movement therein toprovide three distinct and successive discharges of air in such path,air intake means connected to the first blower producing the dischargeinitially encountered by the work in the cooling system to supplythereto a mixture of heated air from within the oven and ambient airexternal to the oven, damper means in said intake means for regulatingthe proportion of the oven-heated and ambient air thus supplied to saidfirst blower, inlet means open outside the oven and connected directlyto the second blower producing the discharge next encountered by thework in its movement through the oven, inlet duct means connected to thethird blower and having an opening for entry of air external to theoven, and refrigeration means connected to the outlet of the thirdblower for chilling the air discharged thereby and caused to flow overthe work in the last of the three cooling stages provided, the chilledair flow permitting the heated work to be brought rapidly to safehandling temperature and the preliminary cooling by the relatively warmand ambient air discharges reducing the work temperature gradually toeliminate destructive thermal shock by such chilled air.

References Cited in the file of this patent UNITED STATES PATENTS1,431,145 Bolling Oct. 10, 1922 1,505,768 Dressler Aug. 19, 19242,110,352 Baker Mar. 8, 1938 2,217,452 Peck Oct. 8, 1940 2,406,821 FoxSept. 3, 1946 2,460,150 Schupp Jan. 25, 1949 2,525,661 Fox Oct. 10, 19502,603,882 Mayer July 22, 1952 2,671,969 Mayer Mar. 16, 1954

